The invention concerns a pipe conduit vehicle which can be moved within the pipe conduit via a transport fluid flow, comprising a housing having an outer surface and with at least one outer ring-shaped sealing element as well with at least one inlet opening and at least one outlet opening on the housing before and behind the sealing element to form a bypass.
Pipe conduit vehicles of this kind, which are designated as pigs, are used for the inspection or cleaning of pipelines which is of primary importance in pipelines in which poisonous or dangerous gases or liquids such as natural gas or liquid oil products are transported.
The above described pipe conduit vehicle can be the cleaning or inspection vehicle itself or can serve as a pulling vehicle or module therefor.
Pipe conduit vehicles usually have a ring-shaped sealing element on their housing for sealing the gap between the housing and the inner wall of the pipe conduit, wherein the corresponding pressure build-up drives the pipe conduit vehicle. The maximum working speed of the pipe conduit vehicle itself or of the cleaning or inspection unit pulled thereby is normally substantially less than the flow velocity of the medium being transported so that the vehicle must move slower than the fluid flow. Since economical considerations prohibit a reduction in pressure within the pipe conduit to reduce the flow velocity when carrying out the necessary repairs or inspection processes, appropriate measures must be taken to reduce the velocity of the pipe conduit vehicle relative to the flow velocity.
Towards this end, a plurality of possibilities have been proposed for reducing the drive force acting on the pipe conduit vehicle, optionally as a pull module for a cleaning or inspection vehicle, by bypassing the sealing element inside the housing.
Flow through the housing is thereby effected via tubes substantially parallel to the longitudinal axis of the pipe conduit vehicle (CA 2042338, EP 0 065 049 B1) or via one or a plurality of openings on the backside of the pipe conduit vehicle (WO 97/17566).
The active flow through cross-sectional area of the bypass can thereby be changed using valve caps in the tubes (EP 0 065 049 B1) or by means of two sealing elements, disposed one behind the other, each having openings which can be aligned with respect to each other by relative rotation of the elements (CA 2042338, WO 97/17566). These changes can be initiated by control and regulation devices which measure the actual speed of the pipe conduit vehicle and regulate same to approach a desired speed through appropriate changes in the flow-through cross-sectional area.
These conventional embodiments have the disadvantage of substantial technical difficulty associated with tubes and with the closing elements needed for each tube as well as poor fluid dynamics for the flow entrance on the rear end.
It is the underlying purpose of the invention to configure a pipe conduit vehicle in such a fashion that a simple and reliable regulation of the speed is possible without having the above mentioned disadvantages.
This purpose is achieved in accordance with the invention with a pipe conduit vehicle of the above mentioned kind in that the at least one inlet opening which can be closed by a closing element is disposed on the outer wall of the cylindrical housing.
This at least one flow opening disposed on the longitudinal side of the housing leads to improved fluid dynamics for the fluid flowing through the housing.
The bypass can be closed and the amount of fluid flowing therein regulated using the closing element for closing the at least one inlet opening to increase the drive pressure on the rear side of the pipe conduit vehicle opposite the direction of travel thereof. The configuration of the inlet opening for the bypass flow and of the closing element therefor in or on the outer wall facilitates reduced adjusting forces for setting the closing element. The closing element is also insensitive to soiling.
The closing element can be advantageously displaced along the outer surface of the cylindrical housing to adjust the fluid volume flowing through the housing. This displacement is preferentially effected continuously to facilitate a precise adjustment of the at least one opening, wherein the closing element itself is advantageously part of the outer surface of the housing and introduced therein.
A preferred embodiment provides for control devices to activate the at least one closing element which can displace the closing element.
Although the adjustment devices can, in principle, be electrical, pneumatic or hydraulic devices are preferred.
The pipe conduit vehicle preferentially comprises measurement and regulation members for regulation of a predetermined desired speed. These measuring members facilitate determination of the current speed of the pipe conduit vehicle and comparison of same to the predetermined intended velocity to regulate to this velocity using appropriate measures.
The measuring members of the pipe conduit vehicle are thereby preferentially in mechanical contact with the pipe conduit wall in order to determine the absolute speed of the pipe conduit vehicle independent of the flow velocity of the fluid. This mechanical contact is preferentially effected via measuring wheels which facilitate a simple construction for determining the velocity with low susceptibility to malfunction.
The measuring members and the control devices are preferentially disposed axially between two sealing elements so that they do not cause turbulence within the flowing fluid.
In an additional advantageous embodiment, the outlet opening of the pipe conduit vehicle is formed on the end side. The transport fluid flowing through the housing with high speed can thereby exit therefrom in a manner exhibiting advantageous flow properties.
The outlet openings on the end side are preferentially delimited with respect to each other by means of radial braces which subdivide the end of the pipe conduit vehicle into smaller symmetrical segments.
The outlet openings can preferentially each be closed by closing elements which can pivot about the braces. This effects a second closing mechanism independent of the closing mechanism on the inlet openings which can e.g. be utilized when the pipe conduit vehicle is stationary or after a predetermined period of time.
The pivot direction of the closing elements is preferentially that of the flow direction of the fluid so that no additional forces must be utilized for closing them.
The closing elements are preferentially secured in the open position via magnetic holders. This guarantees a reliable holding in the open position as well as a rapid release of the closing elements, wherein a release mechanism is also advantageously provided for.
In accordance with a preferred improvement, the closing elements comprise openings which can be closed by spring-loaded flaps. The openings in the closing elements reduce the size of the input flow surface of the closing elements. When the spring-loaded flaps open in response to a pressure wave associated with closing the closing elements, this pressure wave is damped to thereby avoid damage to the closing elements or their abutment surfaces on the housing. When the incoming flow pressure drops below a certain value, the spring located flaps seal the openings in the closing elements.
The invention is described below with reference to the embodiments indicated in the drawing.